Distillation
7 Minutes
Distillation for students: learn how liquids are separated using boiling points, from World War I seawater to pure water. A science lesson in English.
- Why World War I naval soldiers distilled seawater to survive
- How boiling point differences separate homogeneous mixtures
- Distilling salt water in an apparatus and uses of distilled water
What this lesson teaches
Distillation is a method used to separate a homogeneous mixture by heating it until the substance with the lowest boiling point turns into vapor, which is then cooled back into a pure liquid.
How simple distillation works
A homogeneous mixture contains evenly blended substances, such as citric acid dissolved in water. Water boils at 100 degrees Celsius, while citric acid boils at 310 degrees Celsius, giving a difference of 210 degrees Celsius. When heated to 100 degrees Celsius, the water vaporizes first and cools down to a room temperature of 30 degrees Celsius to condense into pure liquid. Simple distillation requires a boiling point difference of at least 25 degrees Celsius, while mixtures with smaller differences require fractional distillation.
Separating salt from seawater
- Seawater contains roughly 35 grams of salt per liter, making it dangerous to drink because excess salt raises blood salt levels and causes kidney failure.
- Pure water boils at 100 degrees Celsius, whereas salt boils at 1465 degrees Celsius.
- When salt water is heated in an apparatus, only the water turns into vapor and rises.
- The vapor passes through a cooling tube, condenses, and collects in a receiving flask as pure water while salt remains behind.
History of the technique
- People in the Babylonian civilization of Mesopotamia first used distillation about 6,000 years ago.
- A baked clay distillation apparatus dating back 5,000 years was found in the Indus Valley near present-day Pakistan.
- Chinese and Arab peoples used distillation about 1,800 years ago to produce alcoholic drinks.
- Naval forces fighting at sea during the First World War used distillation to survive without fresh water supplies.
Uses of distilled water
Distilled water has no minerals, so it lacks normal taste, but it is safe to drink during emergencies because missing minerals can come from food. It is placed inside inverter batteries at home as well as vehicle batteries in cars, buses, and lorries to enable chemical reactions. In the food and beverage industry, manufacturers use distilled water to make sodas and soft drinks.